The present invention relates to a method and a device for detecting a random missing code, and more particularly to a method and a device for detecting a random missing code by applying a delta-sigma (xcex94xcexa3) analog digital converter.
Generally, the performance of an analog digital converter (ADC) is determined by the gauge such as a linearity, a dynamic range, a signal noise ratio (SNR) and the total harmonic distortion plus noise (THD+N). For example, the performance for the integrated circuit (IC) used in the audio coder/decoder (CODEC) is determined by the SNR value, i.e. the real efficient bit of the analog digital converter in a standard testing condition. Moreover, the transformation from a time domain to a frequency domain, i.e. Fourier Transforms, is implemented by the Fast Fourier Transforms (FFT) and the signal noise ratio (SNR) value is determined by a tester according to sampling points and a sampling period, as shown in FIGS. 1A, 1B and 1C.
When a random missing code exists in a chip, the random missing code could not be observed by the foregoing FFT method as shown in FIGS. 2A, 3A and 4A. The random missing code could be observed by magnifying partial sampling period in FIGS. 2A, 3A and 4A, as shown in FIGS. 2B, 3B and 4B. However, the random missing code randomly exists and could not be anticipated, so that the tester would be placed in error.
According to the above-mentioned description, the conventional measuring method has several drawbacks as follows:
1. The random missing code could not be anticipated and the sampling points and periods are limited when the tester is placed in error
2. The conventional measuring method, e.g. the Fast Fourier Transforms (FFT) is time-consuming.
It is therefore tried by the applicant to deal with the above situation encountered in the prior art.
It is therefore an object of the present invention to provide a method and a detecting device for detecting a random missing code rapidly.
According to an aspect of the present invention, the method for detecting a random missing code by applying a delta-sigma (xcex94xcexa3) analog digital converter having a digital filter is provided. The method includes steps of floating an input end of the delta-sigma (xcex94xcexa3) analog digital converter, and detecting an output code outputted from the digital filter of the delta-sigma (xcex94xcexa3) analog digital converter for determining whether the random missing code exists.
Preferably, the random missing code is determined in a time domain.
Preferably, the random missing code is determined via an oscilloscope.
Preferably, the random missing code is determined by the value of the output code when floating the input end of the delta-sigma (xcex94xcexa3) analog digital converter.
Preferably, the random missing code is determined when the value of the output code is a digital value other than 0.
Preferably, the delta-sigma (xcex94xcexa3) analog digital converter further comprises a comparator, a digital analog converter and a low pass filter.
Preferably, the digital filter comprises a plurality of multiplier-accumulators, a delay flip-flop and a coefficient register.
According to another aspect of the present invention, the method for detecting a random missing code is provided. The method includes steps of providing a delta-sigma (xcex94xcexa3) analog digital converter, floating an input end of the delta-sigma (xcex94xcexa3) analog digital converter, and detecting an output code outputted from a digital filter of the delta-sigma (xcex94xcexa3) analog digital converter for determining whether the value of the output code is a specific digital value other than 0.
Preferably, the random missing code is determined by the specific digital value other than 0.
According to another aspect of the present invention, the detecting device for detecting a random missing code includes an amplifier having an input end and an output end, wherein the input end is floating, an adder-subtractor electrically connected to the output end of the amplifier, a low pass filter electrically connected to the adder-subtractor, a comparator electrically connected to the low pass filter, a digital analog converter electrically connected to the comparator and the adder-subtractor, and a digital filter electrically connected to the comparator for outputting an output code, thereby determining whether the output code is the random missing code
Preferably, the digital filter comprises a plurality of multiplier-accumulators, a delay flip-flop and a coefficient register.
Preferably, the random missing code is determined by the value of the output code.
Preferably, the random missing code is determined when the value of the output code is a digital value other than 0.